1. The Field of the Invention
The present invention relates to a transparent bimodal linear block copolymer and its manufacturing method and usage and, more particularly, to a transparent bimodal linear block copolymer and its manufacturing method and usage being characterized by adding two or more charges of an initiator and monomers during polymerization to form a block.
2. Related Prior Art
Generally, the preparation of multiblock copolymer resins from a vinyl aromatic monomer and a conjugated diene monomer involves adding two or more charges of the monomers and an initiator.
According to the prior art, a transparent tapered block copolymer is prepared by a method including the steps of (1) adding one charge of a vinyl aromatic monomer and n-butyl lithium; (2) adding one charge of a vinyl aromatic monomer and a conjugated diene monomer; and (3) adding one charge of a vinyl aromatic monomer (Ref GB 1436812). More specifically, the reaction in the step (2) of the polymerization process forms a copolymer having a tapered block between the polyconjugated diene block and the polyvinyl aromatic block. In this method, the monomodal copolymer having a tapered block to balance its mechanical properties is simple in preparation method but interior in general properties.
On the other hand, EP 242614 discloses a preparation method of block copolymers that includes the steps of (1) adding n-butyl lithium and a vinyl aromatic monomer; (2) further adding n-butyl lithium and a vinyl aromatic monomer; (3) adding a conjugated diene monomer; (4) further adding n-butyl lithium and a vinyl aromatic monomer; and (5) adding a conjugated diene monomer and a vinyl aromatic monomer.
In this method, the polymodal copolymer is prepared by adding three charges of the initiator and at least two charges of monomers to form one tapered block only at the end of the polymer chain.